Bump Billboard in SF: Explained!

So every day on my way to SF i see the billboard promoting Bump. Their 80 million user number is quite compelling but the graph always confused me. I figured it was just standard ‘clip art’ and wondered why they’d show a choppy curve – ie if this is supposed to be a user graph (as it suggests) what are those dips – why were there periods of inactivity. It seemed like a poor graphic choice.

However founder/CEO David Lieb helpfully let me know via Jig that he believes in fact it’s drawn from real Bump data.

via David: it’s actually real data in the graph. number of items shared via Bump per week I think.”

So the question has been answered! And all I’m left wondering is why they used “number of items shared per week” instead of total users to depict their growth cleanly.